During the last two decades much has been learned about the functioning of taste cells through the identification of taste receptors (e.g., T1R's, T2R's), functional markers (e.g., -gustducin, IP3R3, PLC2), and synaptic proteins (e.g., SNAP-25, syntaxin, synaptobrevin, synaptotagmin). Our laboratory has shown that classical synapses and synaptic proteins are associated with Type III cells. Although both small, clear vesicles and large, dense-cored vesicles are present at Type III cell synapses, the nature of their neurotransmitters remains a mystery. The situation with Type II cells is even more inscrutable. No classical synapses have been found associated with Type II cells, yet it is generally accepted that Type II cells transduce bitter, sweet and umami stimuli. In addition, recent studies indicate that Type II cells release ATP as a neurotransmitter. We have previously described putative functional contacts for Type II cells, including large, atypical mitochondria which are present at close appositions between taste cells and intragemmal nerve processes. We propose to examine communication in taste buds by using immunofluorescence and immunoelectron microscopy with colloidal gold labeling or silver-intensified nanogold immunoelectron microscopy to elucidate the nature of functional contacts in taste buds of the mouse. The goals for this application are to answer the following questions: Aim 1. What is the nature of the contacts between Type II cells and nerve processes? Aim 2. Do Type II cells form specialized contacts with other taste cells? Aim 3. What is the nature of the contacts formed by Type III cells with Type II cells and nerve processes? The results obtained from these studies will help to elucidate the basic mechanisms underlying taste, one of the most complex of the senses. These results will provide an important basis for understanding and treating diseases of the gustatory system. Such an understanding of gustation in health and disease will facilitate future studies of other sensory systems and the nervous system in general.